A conventional apparatus for absorbing or damping vibration of a printer, such as a shuttle type dot printer, is disclosed in Japanese Laid-Open Patent Application No. SHO 56-18442.
The print mechanism unit of this printing apparatus is supported on a base of the casing or housing thereof through a vibration absorbing material made, for example, of rubber.
This conventional apparatus has a defect that absorption or damping of the vibration of the unit is insufficient.
Such a conventional print mechanism unit has a print head which moves reciprocatingly in the right and left directions and makes the print mechanism unit a vibrating unit of the apparatus. The vibration absorbing material which supports the print mechanism unit in the casing or housing partially absorbs the vibration caused by this motion.
Moreover, a straight movement of the print mechanism unit in the left and right direction of the print mechanism unit caused by this movement of the print head, produces a component of force in the up and down direction. Further, the vibration absorbing material also moves in a very small circular motion during such vibration.
The weight of the print mechanism unit, the circular movement thereof and the up and down component caused by the vibrations of the print mechanism unit cause vibrations to be transferred to the housing through the same vibration absorbing material, and this in turn causes noise to occur.
To avoid this problem, the conventional vibration absorbing material provides high elasticity, i.e. a high resistance to deformation, in the up and down direction for increasing the stability in this direction.
However, to absorb the vibration caused by the movements of the print head, it is desirable to reduce the resisting force in the right and left directions which is provided by the vibration absorbing material, which is normally in the form of four rubber bodies, such as four feet supporting the print mechanism unit on the housing. To satisfy this requirement, the elasticity of the vibration absorbing material in the right and left directions should be made lower.
However, if the elasticity in the right and left directions of the vibration absorbing material is made lower, the elasticity in the up and down directions is also made lower at the same time, and this is the opposite effect to that which is desired for the best support of the print mechanism unit in the up and down directions, i.e. high elasticity so as to reduce support for the vibrating unit of the apparatus on the base of the housing.
It is not possible to reduce the elasticity of the vibration absorbing material in the right and left directions only, and at the same time either maintain the elasticity in the up and down directions or even increase it where the print mechanism unit is supported by the four rubber elastic bodies.
Therefore, the vibration absorbing material cannot provide a good effect both for providing stable support for the vibrating unit of the printing device on the base of the housing and at the same time absorbing the lateral vibration in the opposite lateral directions.
Further, it is the normal practice with machines which have a vibrating unit which moves relative to the base, such as the print mechanism unit of the shuttle type dot printer, to lock the vibrating unit relative to the casing of the machine when it is necessary to transport the machine. A conventional means for doing this is to provide a threaded hole in the vibrating unit of the machine and an unthreaded hole in the casing or housing, and to provide a bolt which is inserted through the unthreaded hole and threaded into the vibrating unit so as to lock the vibrating unit to the casing. When the machine reaches its desired location, the bolt is removed, and the machine placed on a desk, floor, or other supporting surface. The thus removed bolt, however, is then separate from the housing, and very frequently is misplaced, so that when it is desired to move the machine again, another bolt must be located.